Detection System

Abstract

By repeatedly charging and discharging the battery after manufacturing is complete, it is possible to detect internal short circuits caused by foreign metal particles entering the battery even after manufacturing is complete. [Solution] The detection system includes an electric vehicle 1, an energy storage device 30 mounted on the electric vehicle 1 and including a battery pack 40 having a first battery stack 41 and a second battery stack 42, and a control device 20. The first battery stack 41 has a plurality of energy storage cells 45. The control device 20 controls charging and discharging between the first battery stack 41 and the second battery stack 42, and detects internal short circuits in the plurality of energy storage cells based on voltage drops in the plurality of energy storage cells 45 after charging and discharging.

Description

[Technical Field]

[0001] The present disclosure relates to detection systems. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2016-081758 discloses a nonaqueous electrolyte secondary battery that suppresses the occurrence of internal short circuits by preventing the intrusion of metallic foreign matter into areas that are difficult to dissolve during aging. Specifically, to prevent the intrusion of metallic foreign matter into areas that are difficult to dissolve during aging, at least a portion of the edge of the contact surface between the negative electrode active material layer and the separator is welded.

[0003] More specifically, in the manufacturing process of nonaqueous electrolyte secondary batteries, aging treatment and voltage testing are performed to detect foreign matter within the battery. If metallic foreign matter enters a region where foreign matter is difficult to dissolve, the metallic foreign matter cannot be dissolved and extracted by the aging treatment, and the foreign matter within the battery cannot be detected by the voltage testing. In the nonaqueous electrolyte secondary battery disclosed in JP 2016-081758 A, at least a portion of the edge of the contact surface between the negative electrode active material layer and the separator is welded, thereby preventing the metallic foreign matter from entering the region where it is difficult to dissolve during the aging treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-081758 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even in the nonaqueous electrolyte secondary battery disclosed in JP 2016-081758 A, there is a possibility that metallic foreign matter that was not detected during the aging treatment in the manufacturing process of the nonaqueous electrolyte secondary battery may migrate onto the electrodes due to the movement of the electrolyte accompanying repeated charging and discharging in the field, causing an internal short circuit in the battery.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a detection system that detects internal short circuits caused by metallic foreign matter that has become mixed into a battery even after battery manufacturing is complete, by repeatedly charging and discharging the battery after manufacturing is complete. [Means for solving the problem]

[0007] A detection system according to a first aspect of the present disclosure includes an electric vehicle, an energy storage device mounted on the electric vehicle and including a battery pack having a first battery stack and a second battery stack, and a control device, wherein the first battery stack has a plurality of energy storage cells, and the control device controls charging and discharging between the first battery stack and the second battery stack, and detects an internal short circuit in the plurality of energy storage cells based on a voltage drop in the plurality of energy storage cells after charging and discharging.

[0008] The electric vehicle of the detection system according to the first aspect of the present disclosure further includes a PCU electrically connected to the power storage device, and an SMR disposed between the PCU and the power storage device and configured to enable switchable electrical connection between the power storage device and the PCU, and charging and discharging are performed when the SMR is open.

[0009] When the control device of the detection system according to the first aspect of the present disclosure detects an internal short circuit, it issues an alert to a supplier of the electric vehicle.

[0010] The control device of the detection system according to the first aspect of the present disclosure starts charging and discharging when the SOC of the battery pack exceeds a threshold value.

[0011] In the detection system according to the first aspect of the present disclosure, charging and discharging are performed while the SOC of the first battery stack is in at least one of the ranges of 20% or less and 60% or more. [Effects of the Invention]

[0012] According to the detection system of the present disclosure, by repeatedly charging and discharging the battery after completion of battery manufacturing, it is possible to detect internal short circuits caused by metallic foreign matter that has become mixed into the battery even after battery manufacturing is completed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of an electric vehicle 1 equipped with a detection system according to the present embodiment. [Figure 2] FIG. 2 is a control flow diagram of the detection system according to the present embodiment. [Figure 3] FIG. 4 is a control flow diagram of inter-stack charging / discharging in the control flow of the detection system according to the present embodiment. [Figure 4] FIG. 4 is a control flow diagram of inter-stack charging / discharging in the control flow of the detection system according to the present embodiment. [Figure 5] FIG. 10 is a diagram showing an example of a time transition of the battery stack power amount due to inter-stack charge / discharge control. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated. <Detection system configuration> 1 is a diagram showing a schematic configuration of an electric vehicle 1 equipped with a detection system according to this embodiment. The electric vehicle 1 is, for example, an electric car. The electric vehicle 1 includes a motor generator (MG) 11, which is a rotating electric machine, drive wheels 12, a power control unit (PCU) 13, a system main relay (SMR) 14, an HMI device 15, an ECU 20, and a power storage device 30.

[0015] The MG 11 is, for example, an interior permanent magnet synchronous motor (IPM motor) that functions as both an electric motor (motor) and a generator (generator). The output torque of the MG 11 is transmitted to the drive wheels 12 via a power transmission device that includes a reducer, a differential gear, etc.

[0016] When braking the electric vehicle 1, the MG 11 is driven by the drive wheels 12 and operates as a generator. As a result, the MG 11 also functions as a braking device that performs regenerative braking to convert the kinetic energy of the electric vehicle 1 into electric power. The regenerative power generated by the regenerative braking force in the MG 11 is stored in the power storage device 30.

[0017] The PCU 13 is a power conversion device that converts power bidirectionally between the MG 11 and the power storage device 30. The PCU 13 includes, for example, an inverter and a converter that operate based on a control signal from the ECU 20. When the power storage device 30 is discharging, the converter boosts the voltage supplied from the power storage device 30 and supplies the boosted voltage to the inverter. The inverter converts the DC power supplied from the converter into AC power to drive the MG 11. Note that the PCU 13 may be configured without the converter.

[0018] The SMR 14 is electrically connected to a power line connecting the power storage device 30 and the PCU 13. When the SMR 14 is closed (ON) in response to a control signal from the ECU 20 (i.e., in a conductive state), power can be exchanged between the power storage device 30 and the PCU 13. On the other hand, when the SMR 14 is opened (OFF) in response to a control signal from the ECU 20 (i.e., in a cut-off state), the electrical connection between the power storage device 30 and the PCU 13 is cut off.

[0019] The HMI device 15 is mounted on the vehicle and displays various information (e.g., map information and video content) on a display screen (not shown), and notifies various information (e.g., traffic information, weather information, etc.) by voice or other means. The HMI device 15 includes a display with a touch panel, a speaker, etc. The HMI device 15 outputs to the ECU 20 a signal corresponding to an input to the HMI device 15 by a supplier of the electric vehicle 1.

[0020] The ECU 20 includes a processor 21, a memory 22, and a storage 23. The processor 21 is an arithmetic device such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The memory 22 is a volatile memory (working memory) such as a RAM (Random Access Memory). The storage 23 is a rewritable non-volatile memory such as a flash memory. The storage 23 stores system programs including an OS (Operating System) and control programs including computer-readable code required for control calculations. The processor 21 reads the system programs and the control programs, expands them into the memory 22, and executes them to perform various processes. The ECU 20 may be divided into multiple ECUs for each function. The ECU 20 is an example of a "control device" in the present disclosure.

[0021] Power storage device 30 includes a battery pack 40, a positive electrode line PL, a negative electrode line NL, a power line CL1, a power line CL2, a power line CL3, a power line CL4, a relay R, a resistor Re, and a bidirectional DC / DC converter 60.

[0022] The battery pack 40 includes a first battery stack 41 and a second battery stack 42. The first battery stack 41 and the second battery stack 42 each include a plurality of power storage cells 45 and a monitoring unit 50.

[0023] The plurality of storage cells 45 are electrically connected in series. The storage cells 45 are secondary batteries such as nickel-metal hydride batteries or lithium-ion batteries. The secondary battery is, for example, a battery having a liquid electrolyte between a positive electrode and a negative electrode.

[0024] The monitoring unit 50 has various sensors that detect the states (for example, temperature, current, and voltage) of the multiple storage cells 45. The monitoring unit 50 also functions as a BMS (Battery Management System) that has an SOC function that estimates the SOC (State Of Charge) of each of the multiple storage cells 45, an SOH estimation function that estimates the SOH (State of Health) of each of the multiple storage cells 45, a voltage equalization function that equalizes the voltages of the multiple storage cells in the battery stack, and a communication function. The monitoring unit 50 outputs the detection results to the ECU 20. The monitoring unit 50 has a first monitoring module 51 and a second monitoring module 52. The first monitoring module 51 monitors the multiple storage cells 45 in the first battery stack 41. The second monitoring module 52 monitors the multiple storage cells 45 in the second battery stack 42.

[0025] The positive electrode terminal of the first battery stack 41 and the positive electrode terminal of the second battery stack 42 are connected to a positive electrode line PL, and the negative electrode terminal of the first battery stack 41 and the negative electrode terminal of the second battery stack 42 are connected to a negative electrode line NL.

[0026] The relays R include a first relay R1, a second relay R2, a third relay R3, a fourth relay R4, a fifth relay R5, and a sixth relay R6. The relays R are configured to be able to be opened (OFF) and closed (ON) in response to a command from the ECU 20.

[0027] The first relay R1 is provided on the positive electrode line PL between the positive electrode terminal of the first battery stack 41 and the positive electrode terminal of the second battery stack 42. The power line CL1 connects the negative electrode terminal of the second battery stack 42 to the negative electrode line NL. The second relay R2 is provided on the power line CL1. The power line CL2 connects the positive electrode terminal of the first battery stack 41 and the first relay R1 on the positive electrode line PL, and connects the negative electrode terminal of the second battery stack 42 and the second relay R2 on the power line CL1. The third relay R3 is provided on the power line CL2. The fourth relay R4 is provided on the positive electrode line PL between the positive electrode terminal of the second battery stack 42 and the SMR 14. The power line CL3 connects the positive electrode terminal and the negative electrode terminal of the first battery stack 41. The fifth relay R5 is provided on the power line CL3. The power line CL4 connects the positive electrode terminal and the negative electrode terminal of the second battery stack 42. The sixth relay R6 is provided on the power line CL4.

[0028] The resistor Re includes a resistor Re1 and a resistor Re2. The resistor Re1 consumes power from the first battery stack 41. The resistor Re1 is provided on the power line CL3 between the fifth relay R5 and the negative terminal of the first battery stack 41. The resistor Re2 consumes power from the second battery stack 42. The resistor Re2 is provided on the power line CL4 between the sixth relay R6 and the negative terminal.

[0029] Bidirectional DC / DC converter 60 electrically connects positive electrode line PL and negative electrode line NL. Bidirectional DC / DC converter 60 is configured to be able to detect the voltage input to bidirectional DC / DC converter 60 and to be able to communicate with ECU 20. Bidirectional DC / DC converter 60 causes a power conversion circuit (not shown) included in bidirectional DC / DC converter 60 to perform a boost operation or stop operation in accordance with a control signal from ECU 20. In this way, bidirectional DC / DC converter 60 is configured to be able to boost DC power in both directions between positive electrode line PL and negative electrode line NL.

[0030] In the above embodiment, the power storage device 30 includes a first battery stack 41, a second battery stack 42, a first relay R1, a second relay R2, and a third relay R3. The positive terminal of the first battery stack 41 and the positive terminal of the second battery stack 42 are connected to a positive electrode line PL. The negative terminal of the first battery stack 41 and the negative terminal of the second battery stack 42 are connected to a negative electrode line NL. The first relay R1 is provided on the positive electrode line PL between the positive electrode terminal of the first battery stack 41 and the positive electrode terminal of the second battery stack 42. The second relay R2 is provided between the negative electrode terminal of the second battery stack 42 and the negative electrode line NL. A power line CL2 connects the positive electrode terminal of the first battery stack 41 and the negative electrode terminal of the second battery stack 42. The power line CL2 is provided with a third relay R3. The fourth relay R4 is provided on the positive electrode line PL between the positive electrode terminal of the second battery stack 42 and the SMR 14.

[0031] An electric vehicle 1 having the power storage device 30 of this embodiment can switch the connection between the first battery stack 41 and the second battery stack 42 between a series connection and a parallel connection, similar to the embodiment disclosed in Japanese Patent Application Laid-Open No. 2024-110701. More specifically, in this embodiment, when the first relay R1, the second relay R2, and the fourth relay R4 are closed (ON) and the third relay R3 is opened (OFF) in response to a command from the ECU 20, the connection between the first battery stack 41 and the second battery stack 42 becomes a parallel connection. When the first relay R1 and the second relay R2 are opened (OFF) and the third relay R3 and the fourth relay R4 are closed (ON), the connection between the first battery stack 41 and the second battery stack 42 becomes a series connection. The first relay R1, the second relay R2, and the third relay R3 are controlled by the ECU 20.

[0032] In the above embodiment, the power storage device 30 is provided with a bidirectional DC / DC converter 60 between the first battery stack 41 and the second battery stack 42. A fourth relay R4 is provided in the positive line PL between the positive terminal of the second battery stack 42 and the SMR 14.

[0033] The electric vehicle 1 having such a power storage device 30 can charge and discharge mutually between the first battery stack 41 and the second battery stack 42. More specifically, in this embodiment, when the third relay R3 and the fourth relay R4 are opened (OFF) and the first relay R1 and the second relay R2 are closed (ON) in response to a command from the ECU 20, a closed circuit is formed that includes the first battery stack 41, the second battery stack 42, and the bidirectional DC / DC converter 60. The bidirectional DC / DC converter 60 boosts the voltage of the first battery stack 41 and supplies power to the second battery stack 42. Alternatively, the bidirectional DC / DC converter 60 boosts the voltage of the second battery stack 42 and supplies power to the first battery stack 41. This allows the first battery stack 41 and the second battery stack 42 to charge and discharge mutually through the operation of the bidirectional DC / DC converter 60.

[0034] In the above embodiment, the power storage device 30 includes a fifth relay R5 and a resistor Re1. The fifth relay R5 and the resistor Re1 are provided on a power line CL3. The power line CL3 connects the positive and negative terminals of the first battery stack 41.

[0035] An electric vehicle 1 having such a power storage device 30 can reduce the SOC of the first battery stack 41 by using the resistor Re1. Specifically, when the fifth relay R5 is closed (ON) and the first relay R1 and the third relay R3 are opened (OFF) in response to a command from the ECU 20, a closed circuit is formed by the first battery stack 41 and the resistor Re1. This allows the power of the first battery stack 41 to be consumed by the resistor Re1. Similarly, the power of the second battery stack 42 can be consumed by the resistor Re2.

[0036] In the above embodiment, the battery pack 40 includes the first battery stack 41 and the second battery stack 42, but the present disclosure is not limited to this. The battery pack 40 may include three or more battery stacks. <Detection system control flow> Next, the control flow of the detection system executed by the electric vehicle 1 will be described with reference to FIGS.

[0037] In step S10 shown in Fig. 2, the ECU 20 checks whether there is an instruction to start the detection system. Specifically, the instruction to start the detection system is issued when the ACC power supply of the electric vehicle 1 is ON and the supplier of the electric vehicle 1 instructs the ECU 20 to start the detection system through operation of the HMI device 15. Alternatively, the ECU 20 may further include a communication unit (not shown), and the supplier of the electric vehicle 1 may instruct the ECU 20 to start the detection system using a mobile terminal or the like, thereby turning on the ACC power supply of the electric vehicle 1 and transmitting a signal to start the detection system to the ECU 20. If there is an instruction to start the detection system (Yes in step S10), the processing of the ECU 20 proceeds to step S12. If there is no instruction to start the detection system (No in step S10), the ECU 20 processes step S10 again.

[0038] In step S12, the ECU 20 opens (turns off) the SMR 14. After that, the process of the ECU 20 proceeds to step S14.

[0039] In step S14, the ECU 20 acquires SOC information of the battery pack from the monitoring unit 50. The SOC of the battery pack is the ratio of the remaining capacity to the maximum capacity of the battery pack 40. In the embodiment of the present disclosure, the maximum capacity of the battery pack 40 is the sum of the maximum capacity of the first battery stack 41 and the maximum capacity of the second battery stack 42. The remaining charge of the battery pack 40 is the sum of the remaining battery charge of the first battery stack 41 and the remaining battery charge of the second battery stack 42. The ECU 20 may calculate the SOC of the battery pack 40 from the SOC information of the first battery stack 41 acquired from the first monitoring module 51 and the SOC information of the second battery stack 42 acquired from the second monitoring module 52. After performing the process of step S14, the process of the ECU 20 proceeds to step S16.

[0040] In step S16, the ECU 20 checks whether the SOC of the battery pack 40 is equal to or less than the lower threshold value TH1. If the SOC of the battery pack 40 is equal to or less than the lower threshold value TH1 (Yes in step S16), the ECU 20 ends the processing of the detection system. If the SOC of the battery pack 40 is greater than the lower threshold value TH1 (No in step S16), the processing of the ECU 20 proceeds to step S18.

[0041] In step S18, the ECU 20 checks whether the SOC of the battery pack 40 is greater than the upper limit threshold TH2. If the SOC of the battery pack 40 is equal to or less than the upper limit threshold TH2 (No in step S18), the process of the ECU 20 proceeds to step S24. If the SOC of the battery pack 40 is greater than the upper limit threshold TH2 (Yes in step S18), the process of the ECU 20 proceeds to step S20.

[0042] In step S20, the ECU 20 discharges the battery pack 40 to reduce the SOC of the battery pack 40. More specifically, the ECU 20 instructs the first relay R1, the second relay R2, the third relay R3, and the fourth relay R4 to be opened (OFF), and the fifth relay R5 and the sixth relay R6 to be closed (ON). This causes the power of the first battery stack 41 to be discharged through resistor Re1, reducing the remaining battery capacity of the first battery stack 41. Similarly, the power of the second battery stack 42 is discharged through resistor Re2, reducing the remaining battery capacity of the second battery stack 42.

[0043] In step S22, the ECU 20 checks whether the SOC of the battery pack 40 is lower than the upper limit threshold TH2. If the SOC of the battery pack 40 is lower than the upper limit threshold TH2 (Yes in step S22), the process of the ECU 20 proceeds to step S24. If the SOC of the battery pack 40 is equal to or higher than the upper limit threshold TH2 (No in step S22), the ECU 20 processes step S20 again.

[0044] In step S24, the ECU 20 switches the relays R. Specifically, the ECU 20 closes (ON) the first relay R1 and the second relay R2, and opens (OFF) the third relay R3, the fourth relay R4, the fifth relay R5, and the sixth relay R6. After performing the process of step S24, the process of the ECU 20 proceeds to step S26.

[0045] In step S26, the ECU 20 performs stack-to-stack charging / discharging. "Stack-to-stack charging / discharging" refers to charging / discharging the first battery stack 41 based on the power and remaining capacity of the second battery stack 42. Alternatively, "stack-to-stack charging / discharging" refers to charging / discharging the second battery stack 42 based on the power and remaining capacity of the first battery stack 41. Note that the stack-to-stack charging / discharging controlled by the ECU 20 in step S26 is an example of "charging / discharging" in the present disclosure.

[0046] 3, the control flow of inter-stack charging / discharging in step S26 will be described. In step S50, the ECU 20 boosts the voltage of the second battery stack 42. More specifically, the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the second battery stack 42. In response to the instruction from the ECU 20, the bidirectional DC / DC converter 60 operates the power conversion circuit to boost the voltage of the second battery stack 42. In response to the instruction from the ECU 20 in step S50, the first battery stack 41 is charged with power from the second battery stack 42. After performing the processing of step S50, the processing of the ECU 20 proceeds to step S52.

[0047] In step S52, the ECU 20 checks whether the SOC of the first battery stack 41 has reached the upper limit setting value SP1. If the SOC of the first battery stack 41 has reached the upper limit setting value SP1 (Yes in step S52), the process by the ECU 20 proceeds to step S56. If the SOC of the first battery stack 41 has not reached the upper limit setting value SP1 (No in step S52), the process by the ECU 20 proceeds to step S54.

[0048] In step S54, the ECU 20 checks whether the SOC of the second battery stack 42 has reached the lower limit setting value SP4. If the SOC of the second battery stack 42 has reached the lower limit setting value SP4 (Yes in step S54), the process by the ECU 20 proceeds to step S56. If the SOC of the second battery stack 42 has not reached the lower limit setting value SP4 (No in step S54), the ECU 20 processes step S50 again.

[0049] In step S56, the ECU 20 starts counting the number of cycles n, with an initial value of 0. The number of cycles n indicates the number of charge / discharge cycles of the first battery stack 41 and the second battery stack 42. The number of cycles n is stored in the memory 22 of the ECU 20. After performing the processing of step S56, the processing of the ECU 20 proceeds to step S58.

[0050] In step S58, the ECU 20 boosts the voltage of the first battery stack 41. More specifically, the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the first battery stack 41. In response to the instruction from the ECU 20, the bidirectional DC / DC converter 60 operates the power conversion circuit to boost the voltage of the first battery stack 41. In response to the instruction from the ECU 20 in step S58, the power of the first battery stack 41 is discharged to the second battery stack 42. After performing the process of step S58, the process of the ECU 20 proceeds to step S60.

[0051] In step S60, the ECU 20 checks whether the SOC of the second battery stack 42 has reached the upper limit set value SP2. If the SOC of the second battery stack 42 has reached the upper limit set value SP2 (Yes in step S60), the process by the ECU 20 proceeds to step S64 shown in Fig. 4. If the SOC of the second battery stack 42 has not reached the upper limit set value SP2 (No in step S60), the process by the ECU 20 proceeds to step S62.

[0052] In step S62, the ECU 20 checks whether the SOC of the first battery stack 41 has reached the lower limit setting value SP3. If the SOC of the first battery stack 41 has reached the lower limit setting value SP3 (Yes in step S62), the process by the ECU 20 proceeds to step S64 shown in Fig. 4. If the SOC of the first battery stack 41 has not reached the lower limit setting value SP3 (No in step S62), the ECU 20 processes step S58 again.

[0053] Referring to FIG. 4, in step S64, the ECU 20 boosts the voltage of the second battery stack 42. More specifically, the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the second battery stack 42. In response to the instruction from the ECU 20, the bidirectional DC / DC converter 60 operates the power conversion circuit to boost the voltage of the second battery stack 42. In response to the instruction from the ECU 20 in step S64, the first battery stack 41 is charged with power from the second battery stack 42. After performing the processing of step S64, the processing of the ECU 20 proceeds to step S66.

[0054] In step S66, the ECU 20 checks whether the SOC of the first battery stack 41 has reached the upper limit setting value SP1. If the SOC of the first battery stack 41 has reached the upper limit setting value SP1 (Yes in step S66), the process by the ECU 20 proceeds to step S70. If the SOC of the first battery stack 41 has not reached the upper limit setting value SP1 (No in step S66), the process by the ECU 20 proceeds to step S68.

[0055] In step S68, the ECU 20 checks whether the SOC of the second battery stack 42 has reached the lower limit setting value SP4. If the SOC of the second battery stack 42 has reached the lower limit setting value SP4 (Yes in step S68), the process by the ECU 20 proceeds to step S70. If the SOC of the second battery stack 42 has not reached the lower limit setting value SP4 (No in step S68), the ECU 20 processes step S64 again.

[0056] In step S70, the ECU 20 adds 1 to the number of cycles n stored in the memory 22. After performing the process of step S70, the process of the ECU 20 proceeds to step S72.

[0057] In step S72, the ECU 20 checks whether the number of cycles n is the specified number of cycles N. If the number of cycles n is the specified number of cycles N (Yes in step S72), the process by the ECU 20 proceeds to step S74. If the number of cycles n is not the specified number of cycles N (No in step S72), the ECU 20 again performs the process of step S58 shown in FIG.

[0058] In step S74, the ECU 20 boosts the voltage of the first battery stack 41. More specifically, the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the first battery stack 41. In response to the instruction from the ECU 20, the bidirectional DC / DC converter 60 operates the power conversion circuit to boost the voltage of the first battery stack 41. In response to the instruction from the ECU 20 in step S74, the power of the first battery stack 41 is discharged to the second battery stack 42. After performing the process of step S74, the process of the ECU 20 proceeds to step S76.

[0059] In step S76, the ECU 20 checks whether the SOC of the first battery stack 41 and the SOC of the second battery stack 42 are equal. Here, "the SOCs are equal" includes cases where the SOC of the first battery stack 41 and the SOC of the second battery stack 42 are completely equal and cases where the SOCs are substantially equal. In other words, this also includes cases where there is a difference between the SOC of the first battery stack 41 and the SOC of the second battery stack 42, for example, a difference of 3%. If the SOC of the first battery stack 41 and the SOC of the second battery stack 42 are equal (Yes in step S76), the ECU 20 proceeds to step S28. If the SOC of the first battery stack 41 and the SOC of the second battery stack 42 are not equal (No in step S76), the ECU 20 processes step S74 again.

[0060] Referring again to FIG. 2 , in step S28, the ECU 20 checks whether an internal short circuit has been detected during the processing of step S26. An internal short circuit can be detected, for example, by a method of monitoring cell voltages before and after aging, as disclosed in Japanese Patent Application Laid-Open No. 2005-209528. Specifically, after the processing of step S26 is completed, the electric vehicle 1 ages the battery pack 40 (self-discharge) by leaving it for a certain period of time. The ECU 20 then compares the voltage values ​​of each of the multiple storage cells 45 acquired from the monitoring unit 50 with the initial voltage values ​​of each of the multiple storage cells 45 acquired in advance before stack charging / discharging, and determines whether a voltage drop has occurred. The initial voltage values ​​may be design values ​​recorded in the storage 23 of the ECU 20. If the voltage drop value is, for example, 25 mV or greater, the ECU 20 determines that an internal short circuit (micro-short circuit) has occurred. Alternatively, in step S26, the ECU 20 may continuously monitor the SOC and voltage values ​​of the multiple storage cells 45 and determine whether or not a voltage drop occurs based on the slope of the SOC and voltage values. If the ECU 20 determines that an internal short circuit exists (Yes in step S28), the processing of the ECU 20 proceeds to step S30. If the ECU 20 determines that an internal short circuit does not exist (No in step S28), the ECU 20 ends the processing of the detection system.

[0061] In step S30, the ECU 20 issues an alert to the supplier of the electric vehicle 1. Specifically, the alert is information that an internal short circuit has occurred in a specific power storage cell 45 in the battery pack 40. For example, the ECU 20 issues an alert to the supplier of the electric vehicle 1 by displaying the detection result on a display unit (not shown) of the HMI device 15. Alternatively, the ECU 20 may issue an alert to the supplier of the electric vehicle 1 by having a communication unit (not shown) of the ECU 20 communicate with a mobile terminal owned by the supplier of the electric vehicle 1. After performing the process of step S30, the ECU 20 ends the process of the detection system.

[0062] In the control flow of the detection system according to the embodiment of the present disclosure, the ECU 20 controls the first battery stack 41 and the second battery stack 42 to perform a charge / discharge cycle (step S26 shown in FIG. 2 ). This promotes expansion and contraction of the electrodes in the storage cells 45 and promotes the movement of metallic foreign matter in the electrolyte. When the movement of the electrolyte causes the metallic foreign matter to move onto the electrodes, lithium, for example, precipitates around the metallic foreign matter as a core, and a voltage drop due to an internal short circuit in the battery is detected. In this way, by promoting expansion and contraction of the electrodes in the storage cells 45 after battery manufacturing is complete, it is possible to detect an internal short circuit due to the inclusion of metallic foreign matter in the storage cells 45 that was not detected during battery manufacturing, even after battery manufacturing is complete and before the electric vehicle 1 is used in the market. As a result, it becomes possible to replace a storage cell 45 in which an internal short circuit has been detected before the electric vehicle 1 is delivered to a user.

[0063] In the control flow of the detection system according to the embodiment of the present disclosure, when the SOC of the battery pack 40 is lower than the lower limit threshold TH1, the ECU 20 performs control to terminate the implementation of the detection system (Yes in step S16 shown in FIG. 2). This prevents the electric vehicle 1 from running out of power due to the implementation of the detection system, which prevents the electric vehicle 1 from being unable to run.

[0064] In a charge / discharge cycle (step S26 shown in FIG. 2 ) performed in the control flow of the detection system according to the embodiment of the present disclosure, an upper limit setting value SP1 and a lower limit setting value SP3 are set for the SOC of the first battery stack 41. For example, the SOC range of the first battery stack 41 in the charge / discharge cycle may be set to a first region in which the upper limit setting value SP1 is 100% and the lower limit setting value SP3 is 60%. Alternatively, the SOC range of the first battery stack 41 in the charge / discharge cycle may be set to a second region in which the upper limit setting value SP1 is 20% and the lower limit setting value SP3 is 0%. Furthermore, the SOC range of the first battery stack 41 in the charge / discharge cycle may be switched from the first region to the second region during the charge / discharge cycle. This allows inter-stack charging / discharging of the first battery stack 41 to be performed in a region of SOC 20% or less or SOC 60% or more. As a result, the expansion and contraction of each of the storage cells 45 of the first battery stack 41 is accelerated compared to when the SOC range is not limited. This improves the accuracy of the detection system's detection of internal short circuits caused by the inclusion of metallic foreign matter. The upper limit setting value SP2 and lower limit setting value SP4 for the SOC of the second battery stack 42 can be set in the same way as for the first battery stack 41.

[0065] In the control flow of the detection system in the above embodiment, the ECU 20 controls the first battery stack 41 and the second battery stack 42 to perform a charge / discharge cycle, but the present disclosure is not limited to this. The battery pack 40 may have three or more battery stacks, and the ECU 20 may control the battery stacks to perform a charge / discharge cycle between each of the battery stacks. <Example of battery stack power consumption over time due to charge / discharge control> Fig. 5 shows an example of the change over time in the amount of electric power of the first cell stack 41 and the second cell stack 42 during inter-stack charging and discharging shown in Figs. 3 and 4. In Fig. 5, a solid line L1 shows the change over time in the SOC of the first cell stack 41. A solid line L2 shows the change over time in the SOC of the second cell stack 42.

[0066] At time t0, the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the second battery stack 42 (step S50 in FIG. 3).

[0067] From time t0 to time t11, the first battery stack 41 is charged by power supply from the second battery stack 42. From time t0 to time t11, the SOC of the first battery stack 41 increases, and the SOC of the second battery stack 42 decreases.

[0068] At time t11, the SOC of the first battery stack 41 reaches the upper limit set value SP1 (Yes in step S52 in FIG. 3). As a result, the ECU 20 starts counting the number of cycles n (step S56 in FIG. 3). Thereafter, the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the first battery stack 41 (step S56 in FIG. 3).

[0069] From time t11 to time t12, the first battery stack 41 discharges by supplying power to the second battery stack 42. From time t11 to time t12, the SOC of the first battery stack 41 decreases and the SOC of the second battery stack 42 increases.

[0070] At time t12, the SOC of the second battery stack 42 reaches the upper limit set value SP2 (Yes in step S60 in FIG. 3), after which the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the second battery stack 42 (step S64 in FIG. 4).

[0071] From time t12 to time t13, the first battery stack 41 is charged by the power supply from the second battery stack 42. From time t12 to time t13, the SOC of the first battery stack 41 increases, and the SOC of the second battery stack 42 decreases.

[0072] At time t13, the ECU 20 adds 1 to the number of cycles n. Thereafter, the ECU 20 checks whether the number of cycles n has reached the specified number of cycles N. The ECU 20 repeats the cycle from time t11 to time t13 described above until the number of cycles n reaches the specified number of cycles N.

[0073] At time t20, the ECU 20 confirms that the number of cycles n has reached N (Yes in step S72 in FIG. 4). Thereafter, the ECU 20 instructs the bidirectional DC / DC converter 60 to boost the voltage of the first battery stack 41 (step S74 in FIG. 4).

[0074] From time t20 to time t21, the first battery stack 41 discharges by supplying power to the second battery stack 42. From time t20 to time t21, the SOC of the first battery stack 41 decreases, and the SOC of the second battery stack 42 increases.

[0075] At time t21, the equalization of the SOCs of the first battery stack 41 and the second battery stack 42 is completed. After that, the process of the ECU 20 proceeds to step S28.

[0076] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0077] 1 electric vehicle, 11 MG, 12 drive wheel, 13 PCU, 14 SMR, 15 HMI device, 20 ECU, 21 processor, 22 memory, 23 storage, 30 energy storage device, 40 battery pack, 41 first battery stack, 42 ​​second battery stack, 45 energy storage cell, 50 monitoring unit, 60 bidirectional DC / DC converter, CL1 power line, CL2 power line, CL3 power line, CL4 power line, L1 solid line, L2 solid line, n number of cycles, N specified number of times, NL negative line, PL positive line, R relay, Re resistor, R1 first relay, R2 second relay, R3 third relay, R4 fourth relay, R5 fifth relay, R6 sixth relay, Re1 resistor, Re2 resistor, SP1 upper limit setting value, SP2 upper limit setting value, SP3 lower limit setting value, SP4 lower limit setting value, TH1 Lower threshold, TH2 upper threshold.

Claims

1. Electric vehicles and an electricity storage device mounted on the electric vehicle and including a battery pack having a first battery stack and a second battery stack; a control device; the first battery stack includes a plurality of storage cells; The control device controls charging and discharging between the first battery stack and the second battery stack, and detects an internal short circuit in the plurality of storage cells based on a voltage drop in the plurality of storage cells after the charging and discharging.

2. the electric vehicle further includes a PCU electrically connected to the power storage device, and an SMR disposed between the PCU and the power storage device, the SMR forming a switchable electrical connection between the power storage device and the PCU; The detection system of claim 1 , wherein the charging and discharging is performed when the SMR is open.

3. The detection system according to claim 1 , wherein the control device issues an alert to a supplier of the electric vehicle when the control device detects the internal short circuit.

4. The detection system according to claim 1 , wherein the control device starts the charging / discharging when an SOC of the battery pack exceeds a threshold value.

5. The detection system according to claim 1 , wherein the charging and discharging are performed while the SOC of the first battery stack is in at least one of a range of 20% or less and a range of 60% or more.

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